Foams of silicates and poly(meth)acrylic acids

Abstract

Inorganic-organic foams are obtained by foaming a mixture of (a) a 5 to 60% by weight aqueous alkali metal silicate or ammonium silicate solution, (b) a sufficient amount of a conventional hardener for aqueous silicate solutions, (c) a polymer of (meth)acrylic acid or a copolymer of acrylic acid and methacrylic acid or of (meth)acrylic acid and a copolymerizable monomer containing ethylinic double bonds, the polymer and copolymer being soluble in the aqueous silicate solution, some or all the carboxyl groups of the polymer or copolymer, where relevant, being neutralized by a base and the amount of polymer or copolymer being 0.1 to 30 parts per 100 parts of SiO 2 contained in the aqueous silicate solution, (d) a blowing agent, (e) a surfactant having a foaming action and, where relevant, (f) gelling agent for solidifying the foam before hardening and/or conventional fillers, and allowing the foam to harden. The foams can be used as insulating materials in the construction industry.

What is claimed is: 
     
       1. An inorganic-organic foam which is based on a water-soluble silicate and can be prepared by foaming and hardening a mixture, which can be hardened at room temperature, of (a) a 5 to 60% by weight aqueous alkali metal silicate or ammonium silicate solution,   (b) a sufficient amount of a hardener for aqueous silicate solutions,   (c) a polymer of (meth)acrylic acid or a copolymer of acrylic acid and methacrylic acid or of (meth)acrylic acid and a copolymerisable monomer containing ethylinic double bonds, the polymer and copolymer being soluble in the aqueous silicate solution, some or all of the carboxyl groups of the polymer or copolymer, where relevant, being neutralised by a base and the amount of polymer or copolymer being 0.1 to 30 parts per 100 parts of SiO 2  contained in the aqueous silicate solution,   (d) a blowing agent,   (e) a surfactant having a foaming action and, where relevant,   (f) gelling agent for solidifying the foam before hardening and/or conventional fillers.   
     
     
       2. A foam according to claim 1, which can be produced from a mixture containing water glass, in particular a water glass which has an Na 2  O/SiO 2  ratio of about 1:3.2, as component (a). 
     
     
       3. A foam according to claim 1, which can be produced from a mixture containing a polyacrylic acid having a viscosity of 0.1 to 10 Pa.s as a 10% by weight aqueous solution, as component (c). 
     
     
       4. A foam according to claim 1, which can be produced from a mixture containing a copolymer of acrylic acid and methacrylic acid as component (c). 
     
     
       5. A process for the production of an inorganic-organic foam which is based on a water-soluble silicate by means of a hardener and a surfactant having a foaming action, which comprises foaming a mixture, which can be hardened at room temperature, of (a) a 5 to 60% by weight aqueous alkali metal silicate or ammonium silicate solution,   (b) a sufficient amount of a hardener for aqueous silicate solutions,   (c) a polymer of (meth)acrylic acid or a copolymer of acrylic acid and methacrylic acid or of (meth)acrylic acid and a copolymerisable monomer containing ethylinic double bonds, the polymer and copolymer being soluble in the aqueous silicate solution, some or all the carboxyl groups of the polymer or copolymer, where relevant, being neutralised by a base and the amount of polymer or copolymer being 0.1 to 30 parts per 100 parts of SiO 2  contained in the aqueous silicate solution,   (d) a blowing agent,   (e) a surfactant having a foaming action and, where relevant,   (f) gelling agent for solidifying the foam before hardening and/or conventional fillers, and allowing the foam to harden.   
     
     
       6. A process according to claim 5, wherein a polyacrylic acid which has a viscosity of 0.1 to 10 Pa.s as a 10% by weight aqueous solution is used as component (c). 
     
     
       7. A process according to claim 5, wherein a copolymer of acrylic acid and methacrylic acid is used as component (c). 
     
     
       8. A process according to claim 5, characterised in that an air/CO 2  mixture, which is driven in mechanically, is used as the blowing agent (d).